An infrastructure for supplying a hydrogen-containing gas used as a fuel at the time of power generation is not developed as a typical material infrastructure, so that a fuel cell system typically includes a hydrogen generator including a reformer configured to generate a hydrogen-containing gas from a natural gas or LPG supplied from the typical material infrastructure.
In the reformer, a steam-reforming reaction is typically used. In the steam-reforming reaction, for example, a city gas and steam that are materials are caused to react with each other at a high temperature of about 600 to 700° C. by using a precious metal-based reforming catalyst, such as a Ni-based reforming catalyst or a Ru-based reforming catalyst. Thus, the hydrogen-containing gas containing hydrogen as a major component is generated.
A material gas, such as the city gas, contains a sulfur compound. Since the sulfur compound is a poisoning material especially for the reforming catalyst, it has to be removed in some way. Here, proposed is a hydrogen generator adopting as one removing method a method of removing the sulfur compound by hydrodesulfurization using a recycled hydrogen-containing gas (see PTL 1, for example).
FIG. 8 is a cross-sectional view showing a schematic configuration of a hydrogen generator of PTL 1. In this configuration, a raw fuel is supplied through a lower end surface of a hydro-desulfurizer 3. The raw fuel having been desulfurized in the hydro-desulfurizer 3 is discharged through an upper end surface of the hydro-desulfurizer 3 to be supplied through a complexly curved passage to a reformer 2. The hydrogen-containing gas discharged from the reformer 2 flows through a shift converter 5 and a selective oxidizer 6 to be discharged to the outside of the hydrogen generator.